Download Waagent archive instead of using git repo.
Specify the version in the manifest (system/waagent section)
Add possibility to specify waagent conf file in manifest (system/waagent section)
Update documentation to match changes

Use log_check_call instead of log_call

refactor test on dictionary key
Merge pull request #71 from osallou/development

Download Waagent archive instead of using git repo.
Minor fixes regarding coding style
'os' module has already been imported
Make use of `$PATH` wherever possible